Treatment Of Poultry For Increasing The Feed Conversion Rate Or For Reducing The Incidence Of Ascites

ABSTRACT

The invention relates to a method for the non-therapeutic treatment of poultry for the purpose of reducing the conversion rate of the feed used to raise the poultry. The treatment comprises orally administering at least one glycine compound to the poultry, which glycine compound corresponds to the following formula (I) or to a salt thereof: wherein R 1  and R 2  are independently an alkyl, an alkenyl or a hydroxyalkyl radical containing 1 to 18, preferably 1 to 6 carbon atoms or wherein R 1  and R 2  form jointly together with the N atom a heterocyclic 5- or 6-membered ring. The glycine compound is preferably N, N-dimethylglycine (DMG). The invention also relates to the therapeutic and second medical use of that glycine compound to reduce the incidence of ascites, and to a feed for poultry containing an amount of that glycine compound.

The present invention relates to a method for the non-therapeutictreatment of poultry for the purpose of reducing the conversion rate ofthe feed used to raise the poultry by means of a particular agent, tothe therapeutic and second medical use of that agent to reduce theincidence of ascites, and to a feed for poultry containing an amount ofthat agent.

In the broiler industry for raising poultry, in particular chickens, andespecially broilers, improvements and developments have been madeessentially in the breeding technique for phyletic lines of broilers andin the rearing technique for increasing the growth rate of broilers.Much emphasis is put on the growth rate and the feed conversion rate inthe method of rearing broilers. A high-calorie feed enables to achieve alower feed conversion rate, i.e. a lower amount of feed is required toproduce a certain amount of poultry, but has brought about someproblems. The high growth rate of the poultry during the rearing periodcan for example no longer be followed by sufficient body metabolicfunctions such as the cardiac function, etc., and the imbalance betweenthese two has increased the death rate, thereby lowering the raisingrate and the productivity to cause great economic damage to the broilerindustry.

One essential cause of death of broilers from the imbalance between thegrowth rate and the development of pulmo-cardiac functions is thesyndrome called “ascites”. This syndrome is considered as one of themost important causes of death for broilers. On a world-wide basis theoccurrence level of ascites in commercial meat chickens is estimated at4.7% (Maxwell H. M., Robertson G. W. British Poultry Science 39,203-215(1998)). The primary occurrence of this disease is a hypoxemic conditionresulting from several factors. Hereby the hematocrite concentrationincreases leading to an increased blood viscosity which gives on itsturn rise to a pulmonary hypertension and possibly right heart sidefailure. An immediate consequence of this condition is that the venalpressure increases, leading to liquid migration out of the blood vesselin the abdominal cavities. Broilers growing up in conditions stimulatinghigh growth rates have a natural sensitivity for hypoxemia and ascitesdue to a combination of high oxygen demand (needed for the high growth)and the relatively underdeveloped cardio-respiratory systems of theseanimals. Other factors contributing to this condition of primaryhypoxemia are an insufficient ventilation system, low temperature of theenvironment, breeding on high altitude and an energy rich feed type(Herenda D. C., Franco D. A. Iowa State University Press, Iowa, p. 4-9(1996)).

Another problem is that nowadays feed compositions for poultry are moreand more supplemented with fats from vegetal sources to reduce the costof the feed without compromising the total energy value of the feed forthe animals. As a direct effect of this increased level of vegetal fatin the feed the oxidative stress for the animals increases and leads tohigher mortality level.

In practice, it is of high economical importance to be able to decreasethe feed conversion rate, i.e. the amount of feed required for 1 kg ofbody weight gain, without having to use a (more expensive) feed having ahigher energy value. In this respect Fekete (Fekete S., Hegedus M., SósE. Magyar Állatorvosok Lapja 34(5), 311-314 (1978)) has done tests toverify whether it might be possible to reduce the feed conversion ratenot by increasing the metabolizable energy value of the feed but bysupplementing a poultry diet with pangamic acid (vitamin B₁₅), moreparticularly in an amount of 1000 mg per kg of feed. The resultsobtained by Fekete indicate however that the feed conversion rate wasnot affected by the pangamic acid and was for both the pangamic acidgroup and the control group equal to about 2.5.

As described above, a further important problem when raising broilers athigh growth rates is the quite high incidence of ascites and theassociated mortality. In the examples described in EP-B-0 981 967 thegrowth rate of the broilers was higher than 50 g/day. The high mortalitywhich was due to ascites could be reduced considerably by addingcoenzyme Q to the high-calorie pelletized feed. Coenzyme Q is however acomplex molecule which is quite expensive to produce.

An object of the present invention is therefore to provide another agentwhich enables to reduce the incidence of ascites in poultry, inparticular in poultry raised at a high growth rate.

A further object of the present invention is to provide a new treatmentof poultry which enables to reduce the conversion rate of the feed usedto raise the poultry, i.e. which enables to reduce the amount of feedrequired to produce a certain amount of poultry meat.

In a first aspect, the present invention concerns a method for thenon-therapeutic treatment of poultry for the purpose of reducing theconversion rate of the feed used to raise the poultry, which treatmentcomprises orally administering a glycine compound to the poultry, whichglycine compound corresponds to the following formula I or to a saltthereof:

wherein R₁ and R₂ are independently an alkyl, an alkenyl or ahydroxyalkyl radical containing 1 to 18, preferably 1 to 6 carbon atomsor wherein R₁ and R₂ form jointly together with the N atom aheterocyclic 5- or 6-membered ring.

In a second aspect, the present invention concerns a method for reducingthe incidence of ascites in poultry by administering the same glycinecompound thereto and the use of this compound for the manufacture of amedicament for reducing the incidence of ascites in poultry.

In a third aspect, the present invention concerns a feed for poultrywhich comprises at least 0.001% by weight of said glycine compound.

In a preferred embodiment, the glycine compound is N,N-dimethylglycine(DMG), N,N-diethylglycine, N,N-diethanolglycine, N,N-dipropylglycine,N,N-diisopropylglycine, or a mixture and/or a salt thereof, the glycinecompound being preferably DMG or a salt thereof. N,N-Dimethylglycine(DMG) was first detected in 1938 as part of the active molecule pangamicacid (6-O-(dimethylaminoacetyl)-D-gluconic acid, PA) (Krebs E. T., BeordN. H., Malin R. Int. Red. Med. 164, 18 (1954)). The original report byKrebs declares that PA is always found together with the knownB-vitamins, this fact together with the assigned biological functionswere taken as reasons to account PA as vitamin B₁₅, although no diseasestate can as yet be attributed exclusively to a deficiency of thesubstance. Russian researchers reported that calcium pangamate couldhave a positive effect on the performance of athletes and on thecardiovascular and liver function. Further Russian studies showed thatthe pangamate formula has some influence on the restore of the immunesystem of guinea pigs and rats which were subjected to high intensityX-rays (Nizametidinova, G. Reports of the Kazan Veterinary Institute112, 100-104 (1972)).

U.S. Pat. No. 3 907 869 defines the component calcium pangamate as theester of dimethylglycine and calcium gluconate and describes asadvantages of PA the capability of enhancing oxidative metabolism iscells and tissues and eliminating the phenomena of hypoxia, as well aspromoting lipid metabolism and acting as detoxicant.

As described in the article of Roger V. Kendall and John W. Lawson,“Recent Findings on N, N-Dimethylglycine (DMG): A new Nutrient for theNew Millenium” (2000), calcium pangamate would not be stable undernormal digestive processes and would rapidly hydrolyze to DMG when givenafter oral administration. When describing the known effects of DMGtheir article, these authors thus considered DMG as the active componentof calcium pangamate.

In accordance with the present invention it has now been found that byorally administering DMG instead of pangamic acid to poultry, the feedconversion rate could be reduced (even after having eliminated anytherapeutic effect of DMG) notwithstanding the fact that such areduction of the feed conversion rate was not obtained by Fekete whenadministering pangamic acid to the poultry. This may possibly beexplained by the fact that in the digestive system of poultry pangamicacid might not hydrolyze, or not sufficiently, to DMG. According to thepresent invention it has further been found that orally administeringDMG to poultry considerably reduces the incidence of ascites and theassociated mortality, in particular when the birds are under a highermetabolic stress. Although in the experiment of Fekete also a number ofbirds have died (were also disregarded when determining the feedconversion rate), he has not reported any effect of pangamic acid on themortality. Based on the experiment of Fekete, the advantageous effectsof the present invention on the feed conversion rate and on theincidence of ascites are thus quite surprising.

As mentioned hereabove, the present invention is concerned with a methodfor the non-therapeutic treatment of poultry for the purpose of reducingthe conversion rate of the feed used to raise the poultry by orallyadministering a particular agent to the poultry, to a method or a secondmedical use of that agent for reducing the incidence of ascites inpoultry and to a feed for poultry comprising that agent.

The invention is applicable to any type of commercial poultry operationbut is primarily concerned with commercial chicken (broiler) and turkeygrowing operations. In a commercial chicken and turkey growing operationthe flock is typically under substantial stress. As is well known,normal industry growing conditions include substantial density in theenclosure, for example, a density on the order of about 0.05 m² perchicken or turkey. Further, the ventilation in such commercial growingoperations is often not a precisely controlled operation and thedetermination of appropriate ventilation including both heating andcooling is a very subjective operation. Further, the life span for abroiler ranges from about 40-60 days and the life span for a turkeyranges from 12-24 weeks so that the whole operation from birth to marketin conditions under which growth is achieved is very stressful to theflock. Moreover, to aggravate the problem, growers will typically pushthe limits of recommended industry conditions which simply increases thestress on the flock.

Due to these growing conditions and the high growth rate, the occurrencelevel of ascites and the associated mortality is already quite high inpractice and limits the development of new feeds or production methodswhich causes even more metabolic or oxidative stress. A higher oxidativestress is for example obtained when the feed compositions contain moreunsaturated fatty acids, for example more than 3% by weight or more than4 or even 5% by weight of the feed, whilst a higher metabolic stress isobtained when the birds are made to take up more calories to increasethe growth rate. These fatty acids are either free fatty acids or fattyacids bound for example in di- or triglycerides.

According to the present invention, it has been found thatadministration of appropriate and effective amounts of a glycinecompound corresponding to formula (I) or to a salt thereof, for examplea sodium or calcium salt, and especially DMG or a salt thereof, topoultry being grown under commercial growing operations enables toreduce the incidence of ascites and the associated mortality rates inthe flock. Further, it has been found that administration of suchglycine compound or a salt thereof enables to reduce the feed conversionrate (in the healthy birds, i.e. without taking the advantageous effecton the mortality into account) and thus enables to use the feed moreefficiently. Finally, the oxidative stress related to the presence ofunsaturated fatty acids in the blood stream can be reduced.

The glycine compound administered to the poultry is preferablyN,N-dimethylglycine (DMG), N,N-diethylglycine, N,N-diethanolglycine,N,N-dipropylglycine, N,N-diisopropylglycine, or a salt of thesecompounds, for example a sodium, potassium or calcium salt. The glycinecompound may also comprise mixtures of these compounds and/or of thesalts thereof. The most preferred glycine compound is DMG or a saltthereof.

When the glycine compound is water-soluble, such as DMG, it can be dosedin the drinking water of the poultry. Most preferably, the glycinecompound is however administered via the feed of the poultry.

The basal diet to which the glycine compound is added can be any typicalpoultry diet meeting the nutritive needs of the broiler type bird,including starter, grower and finishing rations. A conventional dietincludes selections among various protein, carbohydrate, vitamin andmineral sources and will generally contain about 12-25% by weight crudeprotein, 0.5-10% by weight crude fat and 2-12% by weight crude fiber.The feed preferably has a crude protein content of at least 18.5% byweight, a crude fat content of at least 4% by weight, a starch contentof at least 30% by weight, and/or a crude fibre content of less than 5%by weight.

The primary component is generally grain and processed grain by-productswhich supply carbohydrates and some protein. Protein meals fromsoybeans, alfalfa, corn gluten, cottonseed, sunflowers and other plantsare often used to supply additional protein to the diet, as are animalby-products. Poultry feed compositions are generally supplemented withvarious vitamins and minerals (usually in the form of a premix to whichthe glycine compound can also be added), and molasses and animal fatsare added to improve palatability and to increase or balance energylevels. They have generally a moisture content of less than 15% byweight and preferably of less than 14% by weight. General reference ismade to National Research Council, Nutrient Requirements of Poultry.Nutrient Requirements of Domestic Animals. National Academy of Science,Washington, D.C. (1994), for a discussion of poultry nutrientrequirements and typical poultry rations for various species and lifephases of poultry, said reference being incorporated herein.

The feed according to the invention has preferably a metabolizableenergy value of at least 11.5 MJ/kg, and more preferably of at least12.0 MJ/kg, the energy value of the feed being preferably smaller than14 MJ/kg, and more preferably smaller than 13.5 MJ/kg. By means of sucha high-calorie feed, high growth rates can be achieved.

The metabolizable energy as referred to herein is obtained bysubtracting the amount of energy as discharged in faeces and urine(waste calorie) from the amount of total energy of the intake feed(total calorie), and ordinary calorimetry may be applied to each feedcomposition to actually obtain the metabolizable energy of thecomposition. In general, the metabolizable energy value of feed forchickens is obtained on the basis of known tables of calorie componentsfor it, and such known tables may be employed herein to obtain themetabolizable energy in question. The metabolizable energy value canmore particularly be calculated by means of the following formula:

AME (MJ/kg)=15.5CP+34.3EE+16.7ST+13.OSu

Wherein: CP=crude protein

EE=ether extract (=crude fat)

St=starch

Su=sugars.

(see Larbier M, Declerq B, (1992) Nutrition et Alimentation desVolailles. INRA, Paris).

The standard (AOAC International) analysis methods are:

-   dry matter: drying-   crude protein: Kjeldahl method-   crude ash: incineration-   crude fat: ether extraction (Sohxlet method)-   crude fibre: Fibertec analysis-   starch and sugars: Luff-Schoorl analysis (polarimetry).    (see Official Methods of Analysis of AOAC International, 16^(th) ed.    The Association of Official Analytical Chemists, Arlington, Va.).

In a preferred embodiment of the invention, the preferred additive rangeof the glycine compound in the finished feed is about 0.001 to 0.5% byweight, preferably about 0.005 to 0.1% by weight. There is no evidencethat use of the higher amounts would cause any toxicity problems intreated poultry; however, the considerations of cost may becomesignificant.

In the method according to the invention, the glycine compound ispreferably administrated to the poultry for 7 days or longer, preferablyfor 14 days or longer, while they are of 10 to 35-days age. The poultryis preferably selected and raised in such a manner that over the periodduring which the glycine compound is administered the feed conversionrate is smaller than 2.50, preferably smaller than 2.45 and morepreferably smaller than 2.40 kg feed/kg body weight gain and/or thatduring this period the growth rate of the poultry is higher than 50g/day, and preferably higher than 60 g/day. The glycine compound it thuspreferably administered to birds which are under metabolic stress sothat the effects of the glycine compound administration are morepronounced.

Experimental Results

The setup of the experiments described below is to assess the influenceof DMG on:

-   -   Performance in model species for fowl: mortality, feed rate        conversion (FRC)    -   Incidence of ascites: PCV, gross necropsy lesions    -   Plasma metabolites: triglycerides (TG), non-esterified fatty        acid (NEFA)

Methodology and Materials

To examine all the effects associated with the supplementation ofdimethylglycine in fowl feed, a test was setup with broilers as modelspecies. In this slaughter test with 64 broiler hens, 14-day oldchickens were bred for 26 days, i.e. till the age of 40 days. At thebeginning of the test the broilers were ad random divided in 16 groupsof 4 specimens. The birds were fed with one type of feed from the firstday on till the end of the test period. The type of feed was attributedon a random basis to the different housings. The animals were setup witha colored ring around their leg for identification purposes within eachhousing. The control feed was based on a commercial broiler crumbleenriched with 5% corn oil to increase the oxidative stress in the feed.Further 1% celite was mixed into the feed as external marker to allowthe determination of the apparent nutrient digestibility. The feed hadthe following composition: 87.65% dry matter, 6.13% ash, 18.05% crudeprotein, 9.13% crude fat, 4.32% crude fibre and 50.01% othercarbohydrates (including 89% starch and 2% sugar). It has a (calculated)metabolizable energy value of about 13.4 MJ/kg.

In the second type of feed 167 mg of DMG was added per kilogram to thesame composition of feed as described for the control feed. Over theentire test period, the broilers consumed on average about 25 mg DMG perbird per day. The housing of the broilers consisted out of circularhousings with an open roof and bottom and with a total surface of0.72m². The material of the fencing was a flexible wire netting with aheight of 1 m and mazes of 2×2 cm and thickness of 2 mm. The bottom wasstrewed with a thick layer of turf with on top a layer of wood-shavings.Feed and water were ad libitum available at all times. The averageenvironmental temperature was maintained at 15° C. to increase theoccurrence of ascites (Shlosberg A., Zadikov I., Bendheim U., Handji V.,Berman E. Avian Pathology, 21,369-382 (1992)). A conventional lightscheme of 23 hours light:1 hour dark was applied Each bird was bloodsampled and weighted 3 times, namely at days 1, 15 and 26. Thehematocrite concentration was immediately determined by means of anultracentrifugation on a sub sample of each blood sample. Next, theblood samples were subjected to a centrifugation and the blood plasmawas kept at −20° C. On this plasma the concentrations of the plasmametabolites: triglycerines and free fatty acid (NEFA: non-esterifiedfatty acids) were determined.

The daily growth during the two periods (between the first and fifteenthday and between the sixteenth and twentysixth day) was calculated foreach surviving animal. The feed uptake for each housing was alsomeasured during both periods. The commercial feed conversion rate wascalculated for each of the housings for both periods (FCRI and FCR II)and for the total growth period. This commercial feed conversion ratewas calculated by dividing the total feed consumption by the weight gainof the birds which stayed alive during the entire experiment, includingalso the feed consumption of the birds that died. To determine only thenon-therapeutic effect of DMG on the feed conversion rate, the actualfeed conversion rate of the living birds was also calculated moreparticularly on the basis of weight gain and the feed consumed by theseliving birds (based on the weight gain of the birds that died, theamount of feed consumed by these birds was detracted from the total feedconsumption).

At the start of the second period a sample of 100 g of manure wascollected. The coefficients for the apparent metabolizability ofmacronutrients and the apparent nitrogen retention was calculated basedon the external marker method with the acid insoluble (celite) asexternal marker

Apparent metabolizability =1−(NF/NV×IV/IF) wherein : NF: percentage ofexamined nutrient in the faeces sample

NV: percentage of examined nutrient in the feed sample

IV: percentage of the indicator in the feed sample

IF: percentage of the indicator in the faeces sample

To determine the above parameters both the faeces and the feed sampleswere analysed on the dry matter, crude ash, crude protein, crude fat andcrude fibre (AOAC, 1980). The carbohydrates were calculated from thedifference between the dry matter content and the rest of themacronutrients as determined by means of the Weende analysis. Thecontent of insoluble ashes (celite) was determined according to theprocedure of Atkinson et al. (1984).

Finally there was also an autopsy on all chickens. First, the carcassweight was determined by dissection of the head, the paws, eviscerationand the deduction of the average feather weight. Next, the weight of thebreast, buttock and thigh muscle were determined. Also the the heart,liver and abdominal fat were measured. Macroscopic lesions related toascites were visually reviewed and described as indicated by Scheele etal. (2003) (Scheele, C. W., Van Der Klis, J. D., Kwakernaak, C., Buys,N., Decuypere, E., British Poultry Science, 44(3), 484-489 (2003)),these were: accumulation of liquid in the abdomen, a hydropericard andright heart dilatation. The latter was quantified by the ascites heartindex (AHI) being the ratio of the the dry weight of the right ventricleto the dry weight of both ventricles after freeze drying.

Results

Ascites was the major cause of death during the test period of 26 days.The mortality and occurrence of ascites were substantially lower in theDMG supplemented group (Table 1 and 2). Next to a massive accumulationof fluid in the abdomen, all these animals showed a distinct right heartventricle dilatation. At the beginning of the second phase of theexperiment the chickens fed with the DMG supplementation showed a higherapparent metabolizability of the dry matter. From the calculatedmetabolic coefficients for the dry matter and the proteins it can beseen that the ability to metabolise both dry matter and proteins seemsto be improved in the DMG supplemented group (Table 3). From the secondperiod on, the DMG supplemented group also showed a significantlyimproved feed conversion and also an increased growth rate. The totalgrowth rate was however substantially not affected so that the improvedfeed conversion has to be explained by a lower feed consumption.

TABLE 1 Influence of oral DMG supplementation on the productionperformance indicators of broilers. DMG Control Mortality (%) 6.25 9.38Ascites (%) 6.25 15.63 Apparent dry matter 65.05 59.59 metabolizabilityGrowth rate (g/d) Phase I (days 1-15) 70 73 Phase II (days 15-26) 87 80Total (days 1-26) 77 76 Commercial feed conversion FCR I (days 1-15)2.23 2.23 FCR II (days 15-26) 2.17 2.33 FCR total (days 1-26) 2.19 2.26Actual feed conversion FCR I (days 1-15) 2.07 2.05 FCR II (days 15-26)2.13 2.33 FCR total (days 1-26) 2.09 2.16

TABLE 2 Ascites heart index for in autopsy examined hearts of the birdsDMG Control Influence DMG (%) AHI, all animals 0.242 0.294 −17.5 AHI,surviving 0.241 0.299 −19.2 animals

TABLE 3 Metabolic coefficients for both dry matter and proteins DMGControl Metabolic ability 91.5 89.4 dry matter (%) Metabolic ability 7369.3 protein (%)

TABLE 4 Influence of oral DMG supplementation on the blood parameters ofbroilers. DMG Control Hematocrite value (vol %) beginning 28.3 27.2after 15 days 31.6 30.6 after 25 days 31.3 30.3 Triglycerine value(mg/dl) beginning 73 90 after 15 days 101 95 after 25 days 51 38 NEFAvalue (mg/dl) beginning 0.29 0.25 after 15 days 0.49 0.48 after 25 days0.60 1.49

In the above experiment, the actual occurrence of the broiler ascitessyndrome of 4.7% (Maxwell H. M., Robertson G. W. British Poultry Science39,203-215 (1998)) was significantly increased by the setup of the test.The inventors could clearly show that there was a significant differencein the occurrence of ascites in respectively the DMG supplemented andcontrol group of animals. Hence, it could be concluded that DMG has aprotective effect on the pathogenesis of ascites. This effect was alsoconfirmed in the increased hematocrite values for the DMG supplied groupof animals. The direct proof of the positive effect of DMG on theascites condition was found during the autopsy tests on the hart of thechickens. For all animals the AHI (Ascites Heart Index)) was calculatedas the ration of the dry weight of the right heart ventricle to the dryweight of both heart ventricles. This parameter gives a clear indicationon the occurrence of right heart hypertrophy (symptom of ascitessyndrome). Significantly higher AHI values were found for the group ofchickens who weren't supplemented with DMG.

Not only was the ascites syndrome positively influenced by DMG, it wasfurther found that the DMG supplementation led to a reduced feedconversion rate, especially during the second growing period. Thecommercial feed conversion rate, which included the therapeutic effectof DMG on ascites and which is very important from a practical point ofview was clearly improved. However, also the actual feed conversionrate, calculated only on the basis of the weight gain and of the feedconsumed by the birds which stayed alive, was clearly improved. (Thesame actual feed conversion rate can also be calculated on the basis oftotal weight gain of all animals, including the birds that died duringthe trial). This proves that DMG has also a non-therapeutic effect onthe feed conversion rate. This non-therapeutic effect was moreovercoupled to an increase of dry matter and protein metabolizability forthe chickens fed with the DMG supplemented diet.

In the blood panel of the animals, substantial differences in theconcentration of triglycerides and significant differences in theconcentration of free fatty acids (NEFA) were detected. The decrease offree fatty acids, with the DMG supplemented group, can be explained byeither an increased extraction of these products from the blood or bythe fact that less NEFA were mobilized from the fat reserves of theanimals. Since DMG also gives rise to an increase in apparentmetabolizability of the feed, it is most likely that the reduced valuesfor the NEFA were due to the fact that there were less NEFA mobilizedfrom the fat reserves of the chickens. This conclusion can be furthersupported by the high levels of triglycerides detected in the bloodsamples of the DMG supplemented group. This leads to the conclusion thatDMG can be important as support for the energy metabolism and thereduction of metabolic stress.

In summary, it was found that the supplementation of 0.001-0.5 wt. %(based on the feed) of the glycine compound, more particularly of DMG orits salts, has a beneficial effect on a disease in fowl called ascites.The DMG supplementation leads to an increase of the hematocrite level sothat the organism of the bird can deal more effectively with limitedoxygen supply to the tissues. Moreover the DMG also plays a role in thereduction of the free fatty acid content in the blood stream which canlead due to the presence of unsaturated bonds in the molecular structureto oxidative stress leading to the death of the animal. This property isimportant in the modern feed formulation technology which uses more andmore vegetal fats to supplement the feed. Further DMG has a distinctinfluence on both the commercial and the actual feed conversion, animportant economic parameter in the cultivation of fowl in general. Thisfeed conversion is directly linked to the effect that a DMGsupplementation has on the apparent metabolizability of both dry matterand proteins. In general it was found that DMG has a positive influenceon the occurrence of ascites in fowl and on the bird's energymetabolism.

1. A method for the non-therapeutic treatment of poultry for the purposeof reducing the conversion rate of the feed used to raise the poultry,which treatment comprises orally administering at least one glycinecompound to the poultry, which glycine compound corresponds to thefollowing formula (I) or to a salt thereof:

wherein R₁ and R₂ are independently an alkyl, an alkenyl or ahydroxyalkyl radical containing 1 to 18, preferably 1 to 6 carbon atomsor wherein R₁ and R₂ form jointly together with the N atom aheterocyclic 5- or 6-membered ring.
 2. The method according to claim 1,wherein the glycine compound is selected from the group consisting ofN,N-dimethylglycine (DMG), N,N-diethylglycine, N,N-diethanolglycine,N,N-dipropylglycine, N,N-diisopropylglycine, or mixtures or saltsthereof, the glycine compound being preferably DMG or a salt thereof. 3.The method according to claim 1 or 2, wherein the glycine compound isadministered via the drinking water of the poultry.
 4. The methodaccording to any one of the claims 1 to 3, wherein the glycine compoundis administered via said feed.
 5. The method according to any one of theclaims 1 to 4, wherein the poultry comprises broiler chickens.
 6. Themethod according to any one of the claims 1 to 5, wherein the glycinecompound is administered during a period to poultry which is selectedand raised in such a manner that over said period the actual feedconversion rate is smaller than 2.50, preferably smaller than 2.45 andmore preferably smaller than 2.40 kg feed/kg body weight gain and/or insuch a manner that over said period the growth rate of the poultry ishigher than 50 g/day, and preferably higher than 60 g/day.
 7. The methodaccording to any one of the claims 1 to 6, wherein the glycine compoundthereof is administered in an amount of between 0.001 and 0.5% by weightof said feed, preferably in an amount of between 0.005 and 0.1% byweight of said feed.
 8. A feed for poultry comprising at least 0.001% byweight, preferably at least 0.005% by weight of a glycine compound,which glycine compound corresponds to the following formula (I) or to asalt thereof:

wherein R₁ and R₂ are independently an alkyl, an alkenyl or ahydroxyalkyl radical containing 1 to 18, preferably 1 to 6 carbon atomsor wherein R₁ and R₂ form jointly together with the N atom aheterocyclic 5- or 6-membered ring.
 9. The feed according to claim 8,wherein the glycine compound is selected from the group consisting ofN,N-dimethylglycine (DMG), N,N-diethylglycine, N,N-diethanolglycine,N,N-dipropylglycine, N,N-diisopropylglycine, or mixtures or saltsthereof, the glycine compound being preferably DMG or a salt thereof.10. The feed according to claim 8 or 9, which comprises said glycinecompound in an amount of between 0.001 and 0.5% by weight, preferably inan amount of between 0.005 and 0.1% by weight.
 11. The feed according toany one of the claims 8 to 10, which has a metabolizable energy value ofat least 11.5 MJ/kg, and preferably of at least 12.0 MJ/kg, the energyvalue of the feed being preferably smaller than 14 MJ/kg, morepreferably smaller than 13.5 MJ/kg.
 12. The feed according to any one ofthe claims 8 to 11, which has a crude protein content of at least 18.5%by weight, a crude fat content of at least 4% by weight, a starchcontent of at least 30% by weight, and/or a crude fibre content of lessthan 5% by weight.
 13. The feed according to any one of the claims 8 to12, which has an unsaturated fatty acid content of at least 3% byweight, preferably of at least 4% by weight and more preferably of atleast 5% by weight.
 14. The feed according to any one of the claims 8 to13, which has a moisture content of less than 15% by weight, preferablyof less than 14% by weight.
 15. Use of a glycine compound and/or a saltthereof for the manufacture of a medicament for reducing the incidenceof ascites in poultry, the glycine compound corresponding to thefollowing formula (I) or to a salt thereof:

wherein R₁ and R₂ are independently an alkyl, an alkenyl or ahydroxyalkyl radical containing 1 to 18, preferably 1 to 6 carbon atomsor wherein R₁ and R₂ form jointly together with the N atom aheterocyclic 5- or 6-membered ring.
 16. The use according to claim 15,wherein the glycine compound is selected from the group consisting ofN,N-dimethylglycine (DMG), N,N-diethylglycine, N,N-diethanolglycine,N,N-dipropylglycine, N,N-diisopropylglycine, or mixtures or saltsthereof, the glycine compound being preferably DMG or a salt thereof.17. The use according to claim 15 or 16, wherein the glycine compound isadded to poultry feed, the resultant feed comprising said glycinecompound in an amount of between 0.001 and 0.5% by weight, preferably inan amount of between 0.005 and 0.1% by weight.
 18. The use according toany one of the claims 15 to 17, wherein the glycine compound isadministered during a period to poultry which is selected and raised insuch a manner that over said period the actual feed conversion rate issmaller than 2.50, preferably smaller than 2.45 and more preferablysmaller than 2.40 kg feed/kg body weight gain and/or in such a mannerthat over said period the growth rate of the poultry is higher than 50g/day, and preferably higher than 60 g/day.
 19. A method for reducingthe incidence of ascites in poultry, comprising orally administering aglycine compound to the poultry, which glycine compound corresponds tothe following formula (I) or to a salt thereof:

wherein R₁ and R₂ are independently an alkyl, an alkenyl or ahydroxyalkyl radical containing 1 to 18, preferably 1 to 6 carbon atomsor wherein R₁ and R₂ form jointly together with the N atom aheterocyclic 5- or 6-membered ring.
 20. The method according to claim19, wherein the glycine compound is selected from the group consistingof N,N-dimethylglycine (DMG), N,N-diethylglycine, N,N-diethanolglycine,N,N-dipropylglycine, N,N-diisopropylglycine, or mixture or saltsthereof, the glycine compound being preferably DMG or a salt thereof.21. The method according to claim 19 or 20, wherein the glycine compoundis administered via the drinking water of the poultry.
 22. The methodaccording to any one of the claims 19 to 21, wherein the glycinecompound is administered via said feed.
 23. The method according to anyone of the claims 19 to 22, wherein the poultry comprises broilerchickens.
 24. The method according to any one of the claims 19 to 23,wherein the glycine compound is administered in an amount of between0.001 and 0.5% by weight of said feed, preferably in an amount ofbetween 0.005 and 0.1% by weight of said feed.
 25. The method accordingto any one of the claims 19 to 24, wherein the glycine compound isadministered during a period to said poultry which is selected andraised in such a manner that over said period the actual feed conversionrate is smaller than 2.50, preferably smaller than 2.45 and morepreferably smaller than 2.40 kg feed/kg body weight gain and/or in sucha manner that over said period the growth rate of the poultry is higherthan 50 g/day, and preferably higher than 60 g/day.